The invention relates to a fluid friction clutch and especially to a fluid friction clutch for a cooling fan of an internal combustion engine.
A fluid friction clutch for a cooling fan of an internal combustion engine is known from Fed. German patent application No. 3,246,783. The clutch comprises a housing provided with fan blades which, together with a rotor arranged in the housing, forms shear gaps in the usual way for the reception of shear fluid. The housing is rotatably mounted by means of a rolling bearing on a shaft driving the rotor, and has a tubular bearing extension piece protruding into the interior of the housing, in which extension piece the outer race ring of the rolling bearing is held. The bearing extension piece is formed integrally on the housing and provides a cylindrical bearing seating into which the outer race ring is inserted directly.
For reasons of simple production and low weight the housing ordinarily consists of aluminum or an aluminum alloy. In this case however it has appeared that by reason of the temperature fluctuations to which the housing is exposed, bearing play can occur if the bearing extension piece is formed integrally on the housing and thus likewise consists of aluminum or an aluminum alloy. Since aluminum has a higher coefficient of thermal expansion than steel, of which ordinarily the outer race ring of the rolling bearing consists, with increasing working temperature the bearing extension piece expands more, whereby bearing play occurs and the life of the clutch is shortened.
In another context it is known to reinforce the bearing seating of a rolling bearing in an aluminum housing with a steel insert in order to lengthen the life of the bearing. However in these constructions the steel insert always forms the bearing seating for the rolling bearing, which necessitates comparatively expensive production methods if low bearing play is required.
The invention is directed towards providing a way in which a housing, consisting of aluminum or an aluminum alloy, of a fluid friction clutch can be connected with the outer race ring of a rolling bearing which rotatably carries the housing, in a constructionally simple manner, namely so that only relatively slight bearing play occurs even in the case of comparatively great temperature fluctuations.